Question

Which of these represents an element
A. Pb
B. PbS
C. Co^2
D. NaCI

Answer 1

Answer :

(a) Pb

Explaination :

As we know,

(a) Pb stands for Lead.

Here, it's a pure element which cannot be made by joining any other elements by any chemical reactions. Therefore, it's not an element.

(b) PbS is a compund which stands for Lead sulphide.

It's made by joining of two elements which are Lead and Sulphur. Therefore, it's not an element.

$\boxed{PbS_{(s)} = Pb_{(s)} + S_{(s)}}$

(c) CO²

CO² is a compund which stands for Carbon dioxide which is made by joining of two elements which are Carbon and Oxygen. Therefore, it's not an element.

$\boxed{C_{(s)} + O_{2(g)} = CO_{2(g)}}$

(d) NaCl

NaCl is a compund which stands for Sodium chloride which is made by joining of two elements which are Sodium and Chlorine.

$\boxed{Na_{(s)} + Cl_{(g)} = NaCl_{(aq)}}$

$\boxed{\bold{Note}}$

Here, the state of matter is given.

(s) for solid.

(l) for liquid.

(aq) for aqueous.

(g) for gas.

The difference between liquid and aqueous is that, liquid is a pure form of any fuild like water. But aqueous means any solution which are dissolved in water like NaCl.

$\huge{\boxed{Element = (a) Pb}}$